2l6 ORGANIC AGRICULTURAL CHEMISTRY 



whey by means of Fehling's solution. It is often, however, 

 calculated from the total solids by subtracting fats, proteins 

 and ash. 



Preservatives 



The preservatives used with milk include formaldehyde 

 (formalin), hydrogen peroxide, boric acid and sodium carbonate. 

 The testing and determination of these belong to the special 

 field of food analysis and will not be discussed in detail. By 

 means of the hydrochloric acid test formaldehyde may be de- 

 tected in I part to 2jo,ooo. Hydrogen peroxide by the para 

 phenylene diamine test may be detected in i part to 40,000. 

 Boric acid by the turmeric paper test may be detected in i part 

 to 8000, and sodium carbonate by hydrochloric acid on the ash 

 may be detected in i part to 2000. Methods of procedure for 

 these tests may be found in books on food analysis such as 

 Leach, Sherman and Hawk. 



Butter 



The questions concerning the two important milk products, 

 butter and cheese, belong more to a special study of dairy chemis- 

 try or food analysis than to a general discussion of agricultural 

 chemistry. In addition, therefore, to what has already been 

 said in regard to the particular milk constituents characterizing 

 these products, only a few facts will be given in regard to their 

 general composition. 



Butter consists principally of the milk fat with a part of the 

 other constituents of milk that are separated with the fat. 

 The separated fat is subjected to churning and working opera- 

 tions by which the fat is pressed together and mostly freed 

 from the liquid known as buttermilk, when it takes on the 

 appearance of ordinary butter, salt being added as flavoring 

 and as a preservative. The average composition of butter 

 may be given as follows, according to McKay and Larsen 

 (Iowa) : 



